Coal hole

I liked the decorative quality of this metal lid, but I was wondering why a drain cover would need glass panels. A quick google of Hayward Brothers revealed the answer - this isn't covering a drain but a 'coal hole' - much more interesting. Thinking about it the glass should have been a clue, as should the very similar looking one just a bit further up the same street, and also on the pavement outside another grand old house. My powers of deductive reasoning were obviously focused elsewhere at the time ;)